1. Field of the Invention
The present invention relates to a vaporization source for vacuum evaporation for use in a molecular beam epitaxy apparatus, etc.
2. Description of the Prior Art
As disclosed in U.S. Pat. No. 4,137,865, the fundamental structure of a vaporization source for vacuum evaporation has a construction wherein a crucible which contains a source substance being a molten metal is laterally supported by a prop, a heating source such as resistance heating means or radio-frequency induction heating means is disposed around the crucible, and radiant heat shield plates are arranged around and under the heating source and are surrounded with an outer wall.
In the vaporization source for vacuum evaporation thus constructed, the source substance heated by the heating source turns into the form of molecular beams, some of which directly fly out of the opening of the crucible being a jet port and the others of which adhere to the wall surface of the crucible and vaporize therefrom again. In such a case where the temperature of the wall surface of the crucible is lower than the vaporization point of the source substance, this source substance adheres and deposits to the crucible wall surface. When the source substance adhered to the wall surface drops, the bumping phenomenon in which the source substance flies out in the form of particles takes place. When the grains adhere to an evaporated thin film, they form the cause of defects in the film.